Magnetic device



May 12, 1931.

R. R. BATCHER MAGNETIC DEVICE Filed April 27. 1929 I INVENTOR W ATT RNEYcoste Patented May 12, 1931 PATENT orrlca mm a. imrcrmn, ornorms, NEWroux momma rav oli 1 Application filed April 27, 1929. Serial No.358,732.

. My invention relates to improvements in magnetic-devices generallyand, while not limited in its apphcation to any special type of magnet,is particularly adapted for'use 6 and may be a plied with materialadvantage to the form electro-magnet now commonly employed in loudspeakers of the dynamic n such speakers, the electro-magnet con- 10stitutes the principal item of expense, owing to its rather unusualsize, the amount of copper and iron employed and the time and laborrequired in its construction. The pole-pieces of this type of magnet areof such formand so related as to provide a narrow annular gap betweenthem, in which the movable coil, carried by or otherwise secured to thediaphragm of the speaker, is located, free to vibrate clear of the wallsof the gap. 7 29 In order tobrin the pole pieces into the requiredrelation to orm the annular gap, it has heretofore been the practice toemploy a heavy iron pot-like casing or cylinder suitably proportioned toenclose the magnet core proper and the winding thereon. This cylindricalcasing is closed at one end and the closed end is bolted or otherwisesecured in centered relation to the core proper.

A removable cover plate is provided for W the op osite end of the casingand centrally thereof an opening is formed of a diameter to admit thefree projecting end of the core proper and give the necessary clearancefor the movable coil.

I Ordinarily thi's cylindrical casing with one end closed, is formed as,a heavy casting and both it, and its attached parts,the core proper andapertured cover platemust be carefully and. accurately machined toprovide the required narrow'annular gap for the movable coil, which ismounted free to vibratetherein with just sufficient clearance to avoidtouching either wall.

Recognizing that the bulk and welght, plus the labor and material costs,are serious d1sadvantages of the above described structure,

I have devised an improved construction in 'which many of theohjeetional features are entirel avoided and a considerable saving in fle cted, without loss of efiioiency.

. In carrying my invention into efl'ect, I first dispense with the heavycast iron pot-like enclosing casing'and substitute for it comparativelylight steel stamped up members, two of which, exact duplicates of eachother, combine to form the casing and, excepting the necessary punchedbolt holes therein, such members, without requiring machine work of anykind, are complete and ready for immediate assembly in a speaker unit,on leaving the stamp press.

As a lighter weight and less costly substitute for the cast, drilled andmachined cover plate heretofore employed, I form the same of crossed,twin rectangular plates of comparatively light steel strip and again,excepting the necessary punched bolt holes and central openingtherein,these plates are ready for assembly on leaving the stamp press.

A convenient and effective form of mounting or support for the assembledmagnet, diaphragm, etc., is found in the use of a stamping, similar inall respects to the above mentioned members I employ as the enclosingcasing and to extend one of the poles of the magnet. Thus applied, itserves all requirements without change or modification of any kind.

The accompanying drawings will serve to illustrate a constructionsuitable for carry- I ing my invention into effect but I do not wish tobe understood as limiting myself to the same as various changes may bemade therein or other forms employed without departing from the spiritand scope of-the invention, as outlined in the appended claims.

In the drawings- Fig. 1 is a view in elevation, partly in section, of awell known type of dynamic speaker, showing my invention applied;

Fig. 2 is a vertical section on the line a s' of Fig. 1; t

Fig. 3 is a rear elevation thereof, and

Fig. 4 is a view in perspective showing the assembly of the stamped upmembers.

Referring now to the drawings, a wellknown dynamic type of loud speakeris shown for convenience in illustrating the application of myinvention, but it will be understood that other types may be employed,if preferred.

In the speaker shown, a large electro-magor otherwise suitably connectedto a diaphragm 7. The diaphragm is shown mounted in a skeleton metalframe 8, bolted to the magnet casing.

In bringing the pole-pieces of the magnet into relation to form theannular gap, I employ two approximately U-shaped members 9, 9, stampedup from comparatively thin strip steel and arranged one within the otherto form in efi'ect a square box, closed at one end and open at theother, the box thus 'formed being of such size as to completel enclosethe magnet core proper andits win ing. The members 9, 9, are exactduplicates and, as assembled, to form the box-like casing, are arrangedat right angles to each other, as best shown in Fig. 4. 'At the closedend of the casing, the members are bolted in centered relation, solidlyto the core of the magnet, as indicated at 10 and are punched for theinsertion of additional bolts 11, 11, which secure the members together.

At the open end of the casing, the ends of the members are bent overforming terminal flanges 12, 12, etc., and bolted to these flanges thereis aremovable cover formed of crossed twin rectangular plates 13, 13,which are each provided with a central opening 14, of such diameter asto closely encircle the projecting end 4 of the magnet core, leavingonly clearance spacein the annular ap thus formed between the polepieces for ree movement of the movable coil 6.

As a convenient mounting or support for the electro-magnet, thediaphragm and its carrying frame, I utilize a stamped up member 15,similar in all respects to the stampings employed in forming thebox-like casing described and bolt the same to the casing, asindicatedat 16, 16, and shown in Figs. 1 and 3.

The U-shaped mounting or support 15, provides amplehousing for thetransformer 17, which is secured therein by small angle irons and bolts,as indicated at 18, 18. v

The circuit connections form no part of the present invention, and itwill not, therefore, be necessary to describe the same in detail.

The advantages of the invention will be obvious from the foregoingdescription. Eliminating the heavy cast iron pot-like casing with itscast cover and the time and labor necessary in machining both toproduce, with required accuracy, the narrow annular up for the receptionof the movable coil eects a material saving in cost and also in theweight of the structure, as a comparatively light gage steel servesevery purpose without loss of function or efliciency. Furthermore, theutilization of one of the stamped members of the casing as a mounting orsupport results in an additional saving in cost and enables the speakerto be firmly secured in a receiver cabinet in position with thediaphragm paralleling the usual screened opening therein.

In addition to the foregoing, there are various other minor advantageswhich will be apparent without further comment.

While the present description has been confined to the application ofthe invention to an electro-magnet, it will be understood that it isequally applicable without material modification, to a permanent type ofmagnet and may be so used, if desired.

Having thus described my invention, What I claim is:

1. In an electro-magnet comprising a core and a coil wound thereon,means for extending the core to bring the pole-pieces thereof intorelation to form an annular gap between them, the said means consistingof 'a plurality of shaped strip members secured to the core and arrangedin nested relation to form an enclosing casing for the magnet winding.

2. In an electro-magnet comprising a core and a coil wound thereon,means for extending the core to bring the pole-pieces thereof int-orelation to form an annular gap between them, the said means consistingof a plurality of strip members approximately U-shaped, secured to thecore and arranged in nested relation, to form an enclosing casing forthe magnet winding.

3. In an electro-magnet comprising a core and a coil wound thereon,means for extending the core to bring the pole-pieces thereof intorelation to form an annular gap between them, the said means consistingof a plurality of strip members approximately U-shaped, secured to thecore and arranged in nested relation, and a plate apertured to encirclethe core and combining with the strip members to form an enclosingcasing for the magnet winding.

4. In an electro-magnet comprising a core and a coil wound thereon,means for extending the core to bring the pole-pieoesthereof intorelation to form an annular gap between them, the said means consistingof twin strip members approximately U-shaped secured to the core andarranged at right angles to each other in nested relation, and a plateapertured to encircle the core and combining with the strip members toform an enclosing casing for the magnet winding.

v5. In an electro-magnet comprising a core and a coil wound thereon,meansfor extending the core to bring the pole-pieces thereof intorelation to form an annular gap between them, the said means consistingof twin members suitably shaped and arranged in nested relation at rightangles to each other, the ends of the said members being bent over toform flanges, and twin plates apertured to encircle the core andcombining with the strip members to form an enclosing casing for themagnet winding.

6. Means for extending the core of an electro-magnet, which consists oftwin strip members secured to the core to form a continuation thereof,the said members being approximately U-shaped and arranged at rightangles to each other in nested relation to form an enclosing casingaround the magnet winding.

7. Means for extending the core of an electro-magnet, which consists oftwin strip members secured to the core to form a continuation thereof,the said members being approximately U-shaped and arranged at rightangles to each other in nested relation to form an enclosing casingaround the magnet winding, and a suitable support for the encased magnetserving as a housing for an additional circuit element.

I aflix my signature.

RALPH R. BATCHER.

